1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, a copier, a printing machine and the like using electro-photographic process, and more particularly, it relates to an improvement in a disassembling/assembling ability of electric component units to an apparatus main body and an improvement in contact connections.
2. Related Background Art
A construction of a conventional image forming apparatus will now be described with reference to FIGS. 13 and 14. FIG. 13 is a view for explaining a condition that a conventional high voltage unit is incorporated into an apparatus main body, and FIG. 14 is a view for explaining an assembled construction of the conventional high voltage unit and a drive unit.
An image forming apparatus shown in FIG. 13 is a four-color printer using electro-photographic process and includes image forming portions 901Y, 901M, 901C and 901K for yellow, magenta, cyan and black colors, respectively. These image forming portions 901M to 901K are incorporated into a drive unit 902 having high voltage bias applying means. The drive unit 902 includes gears for driving electrifying means, developing means, photosensitive drums and drive rollers of intermediate transferring belts (all are not shown) provided in the image forming portions 901Y to 901K, and, in the illustrated embodiment, the drive unit forms a part of a frame of the main body.
The drive unit 902 receives an electric power from a high voltage unit 903 as an electric component unit. The high voltage unit 903 has a high voltage circuit substrate and has contacts to be connected to the main body frame side within the image forming apparatus. The high voltage unit 903 is connected to a power supply unit 904 for supplying power to various parts of the image forming apparatus and a record controlling system 905 of the image forming apparatus. Incidentally, in the drawings, to clarify the understanding, wires between the electric component units are omitted from illustration. Further, contact portions 906Y to 906K of the high voltage unit 903 are contacted with high voltage connection portions of the drive unit 902 with predetermined pressure, thereby transmitting the electric power.
Next, connection between the drive unit 902 and the high voltage unit 903 is illustrated in FIG. 14 in detail. The high voltage unit 903 is positioned with respect to the drive unit 902 so that bosses and holes are fitted together at positioning portions 907 and 908 and a contact spring 909 of the high voltage unit 903 is contacted with a contact plate 910 of the drive unit 902 with predetermined contact pressure. Further, a contact spring 912 to a secondary transferring contact plate 911 of a secondary transferring portion (not shown) is provided on a back surface of the high voltage unit 903. Furthermore, independently from the positioning, the high voltage unit 903 is secured to the main body frame by fastening means such as screws at attachment portions 913 to 916.
However, in the image forming apparatus having the above-mentioned construction, when the high voltage unit 903 is attached, if the positioning portions 907 and 908 are tried to be aligned, since the electric component unit is not supported at all, the unit becomes unstable and is frequently supported with inclination toward directions 803 and 804, and, thus, there arose a problem that it is very difficult to align to the positioning portions 907 and 908. Under such a condition that the positioning is difficult, if the high voltage unit 903 tries to be forcibly assembled, as it is, the contact spring 909 may ride on the opposite surface of the contact plate 910 or the contact spring 909 itself may be buckled from its tip end to deform and/or damage the contact spring.
In order to avoid the above problem, although there has been proposed an arrangement in which a coil spring (not shown) is incorporated so that is expanded and contracted in an acting direction (up-and-down direction in FIG. 14), since the horizontal positioning of the high voltage unit 903 is insufficient, there frequently arose inconvenience that the coil spring rides on a member between the contacts.
Further, although the high voltage circuit substrate of the high voltage unit 903 can be assembled as a unit, in a case where the substrate has a laminated construction, when high voltage output is provided on the substrate at a position farthest from the high voltage connection portion of the drive unit 902, there arose a disadvantage, in design, that wiring of a cable and the like such as high voltage introducing means to the main body becomes very complicated and difficult. Further, when the connection of the high voltage unit 903 tries to be effected positively, in view of reliability, a press-contact terminal may be used in place of the contact spring 909. If doing so, the circuit substrate must be assembled to the frame directly in the main body assembling line, with the result that it is very difficult to assemble the circuit substrate and peripheral portions thereof as a unit, and the assembling cost and disassembling cost are increased considerably (although an adequate function can be achieved).